1. Field of the Invention
The present invention relates to a three-dimensional graph plotting system. More specifically, the invention relates to a three-dimensional graph displaying system capable of plotting and outputting a three-dimensional graph by processing two-dimensional data at high speed.
2. Description of the Related Art
Conventionally, such a three-dimensional graph displaying system is incorporated in an information processing system as a statistic application program and frequently used as one means for visually displaying data. For the portion which is hidden and not visible as displayed on the output device, such a three-dimensional displaying system has the capability to display such hidden data by rotating the whole graph.
In order to realize the function of plotting the three-dimensional graph with rotation, it is typical to perform a polar coordinates transformation process of the plotting data or a hidden line control process (erasing process of the plot line seen at a further back side) internally in the program.
Namely, in the polar coordinates transformation process, polar coordinate values of respective ones of individual polygonal pole or cylindrical three-dimensional graph images forming the three-dimensional graph are temporarily stored in a memory and are re-calculated depending upon the rotation angle. In the case of the polygonal pole three-dimensional graph image, polar coordinate values for all eight corners are required to be stored in the memory. On the other hand, in the hidden line control process, the positional relationship of the individual polygonal pole or cylindrical three-dimensional graph image with respect to other three-dimensional graph images in terms of which should be seen at the front and the plot line at the back side position is erased.
Since the above-mentioned conventional three-dimensional graph plotting system requires the three-dimensional polar coordinates transforming process or the hidden line control process after rotation of the coordinates, the program becomes special and complicated. As a result, the execution program becomes extensive, causing a lowering of speed in the plotting process or makes maintenance difficult. Also, in the three-dimensional coordinates transformation process, since the amount of plot data becomes large, the work memory and so forth or the memory required in the system becomes large.